In the field of document cameras, it is desirable for an apparatus to capture real-time video streams with the highest clarity possible with zooming-in and zooming-out capability. Prior art of this field have achieved zoomable video directly output to video projectors with video resolution normally in Video Graphics Array (“VGA”) range of 640×480 or Super VGA (SVGA) 800×600 display resolution range and rarely can reach a resolution as high as 1920×1280 without drastically increasing the cost needed to build such as device.
Such a limitation often comes from the limited resolution of video display projectors and the processing capacity of the electronic components which must support the document camera's ability to directly out put analog video signal to the projector. In order for a document camera based on prior art to capture real-time video with high resolution images, high quality tele-focal lens assembly must be employed to zoom in and/or out on the object of interest to compensate the limitation in the electronic circuitry responsible for sensing, generating, and outputting frames of images in a video stream. Such limitation in the electronic circuitry of document cameras based on prior art makes it unsuitable for capturing high resolution still images required for document archiving, copying and display applications. The necessary employment of an optical lens assembly makes it mandatory for these document cameras to often have elaborate motorized housing for the lenses, which results inevitably in relatively heavy structural configurations requiring considerably sized bottom panels serving as both a stabilizing plate and a housing for the electronics. Due to such reasons, these document cameras take away significant desktop space and have less than desirable portability. As an example, a prior art digital document camera is commercially available from an unbranded international OEM supplier, is shown in FIG. 1.
Other document scanning prior art methods teach methods of flatbed scanners or scanning assembly working in conjunction with a motorized document feeder to capture high resolution images often in the range of 150 dpi to 600 dpi range. FIG. 2 shows a typical flatbed scanner apparatus, such as a ScanJet 5590 Digital Flatbed Scanner by Hewlett Packard. However, such an apparatus must require a platen of certain minimum dimensions, which can accommodate various sizes of commonly used paper, and must have significant height in order to accomplish the scanning functions in their enclosed housing of the various mechanical and electronic scanning components. As the size of paper to be scanned gets larger, the size of the traditional scanners will also have to be larger. Such an apparatus is not space efficient and often has poor portability.
Additionally, prior art scanners do not have any ability to capture real-time video of any objects, and almost impossible to capture any images of three dimensional objects. These scanners select a sub-area within a preview image of the document ahead of time, which requires a pre-scan of the document and therefore takes longer than a desirable amount of time. Scanning of paper documents is also time consuming ranging from approximately 6 seconds in highly expensive professional grade scanners to 12 to 80 seconds in order to finish a Legal sized document.
U.S. Pat. No. 6,965,460 B1 describes a look-down digital imaging device having a linear sensor for imaging a raster line of an original image placed substantially below the look-down device, and achieving the capture of a relatively high resolution image by sweeping a raster line across the scan area in the same fashion of a flatbed scanner, also with the aid of a video camera device housed in the same housing unit. Although the apparatus described in this reference suspends the imaging unit on a stand, the time cost, electronic components, mechanical components, and potentially motorized components necessary in tilting and sweeping the raster line across the entire surface area of a target while capturing the reflected linear line sequentially one line at a time, were not fully disclosed. It is conceivable that the scanning time consumed to sweep the raster line across the entire scanning area can be similar to and not significantly better than the time required by commercial available flatbed scanners. However, this reference does not address the need for speed efficiency gains over existing flatbed scanners. The employment of a second assisting video camera required in the prior art increases the volume and weight of the housing unit. In another aspect, by requiring the inclusion of multiple components, such as the zoomable lenses, the linear scanning components, and the video camera, this reference is not advantageous in achieving sufficient compactness in possible embodiments of the apparatus described.
U.S. Pat. No. 6,540,415 B1 describes a stand with a hinged housing unit which can hold in place a fully self-contained, ready-made, commercially available digital camera, which closely resembles a point-and-shoot camera. As commercial digital camera products vary in design form factors, output connection technologies, control button accessibilities, and built-in imaging functions, this reference may not be adaptable to many possible variations to make a commercial embodiment practical or advantageous in real life applications.